Better way to identify if a viewController was reached by popping the navigationController or using the tab-bar

Question

Attempt to clarify: I would like to be able to differentiate between the two following scenarios:

a viewController's view becoming active as result of a pop.
a viewController's view becoming active as result of tabBar-navigation

In the app I'm working on I need to know if a viewController was presented due to its navigationController being popped or not. I had a look at this post and thought I had found the solution by simply calling:

BOOL wasReachedByPopping = !self.isMovingToParentViewController;

in my viewWillAppear: method

This works fine for most cases, but will unfortunately give a false positive when switching navigationControllers via a tabBarController. I've been thinking about adding a BOOL to my viewController called pushedNewController that will be set to YES prior to pushing.

self.pushedNewController = YES; // whenever I plan to push

This should work just fine, but I am really unhappy about having to base this on something as messy as long-lasting BOOL states. Anyone has a better approach to identify whether the viewController was reached by a pop or not?

Edit: I appreciate the effort below, but it seems they just offer the exact same functionality I already have. There are no methods there differentiating between being popped to or moved to through tab-bar-navigation. Seems I will have to settle on an internal BOOL to store whether the viewController requested a push or not. I set it up the following way, for anyone interested:

- (void)viewDidDisappear:(BOOL)animated{
    self.disappearedDueToPush = (self != [self.navigationController.viewControllers lastObject]);
}

score 1 · Answer 1 · answered Feb 05 '14 at 13:24

Have you looked at UINavigationControllerDelegate methods:

– navigationController:willShowViewController:animated:
– navigationController:didShowViewController:animated:

These are called when a view controller is pushed on or popped off your nav stack.

See Apple docs for more info.

score 1 · Answer 2 · answered Feb 05 '14 at 13:26

1

You want UINavigationControllerDelegate, specifically, the didShowViewController: method. Here's a usage example:

- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    if (viewController == self) {
        NSLog(@"%@",viewController);
    }
}

answered Feb 05 '14 at 13:26

Mick MacCallum

129,200
40
280
281

1

Thanks, but from what I can see this is called both when the viewController is popping to a viewController and when accessed through a tabbarcontroller. In other words the exact same states I achieve checking the `!self.isMovingToParentViewController;` in my viewWillAppear. I need to differentiate between being popped to, and moved through by the tab-bar... – T. Benjamin Larsen Feb 05 '14 at 14:57

score 0 · Answer 3 · answered Feb 05 '14 at 13:26

You can use this if conditon for whether the viewcontroller is popped or not!!!

if ([self.navigationController.viewControllers indexOfObject:viewControllerObj] == NSNotFound)
{
    [self.navigationController pushViewController:viewControllerObj animated:YES];
}
else
{
    [self.navigationController popToViewController:viewControllerObj animated:YES];
}

score 0 · Answer 4 · answered Feb 05 '14 at 13:38

0

Try this...

if ([self.navigationController.viewControllers containsObject:<Your View Controller>])
{
    NSLog(@"It is Pushed");
}
else
{
    NSLog(@"It is Poped");
}

answered Feb 05 '14 at 13:38

Rajesh Choudhary

1,340
8
12

score 0 · Accepted Answer · answered Feb 05 '14 at 16:05

So to recap, there seems to be no way outside storing the fact that the push was performed as a state. From the answers provided below, this state can be set by implementing the UINavigationControllerDelegate and using the navigationController:willShowViewController:animated:method:

- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated{
    self.disappearedDueToPush = !(viewController == self);
}

If implementing the delegate seems a bit heavy handed (it did to me) you might up the following in your viewDidDisappear method instead:

if (self != [self.navigationController.viewControllers lastObject]){
    self.disappearedDueToPush = YES;
}

This made more sense to me as the reverse logic (and checking towards the fact) is performed in the viewWillAppear method.

Better way to identify if a viewController was reached by popping the navigationController or using the tab-bar

5 Answers5